I can't seem to get a smart group to update. I've replicated this issue in the sandbox and in 9019.
Steps to replicate:
1) Do a search
2) Create a smart group with all contacts from that search
3) Update the search criteria for the smart group and search again
4) Select 'Update smart group' from the more actions menu
5) An error appears - The screen is blank in the sandbox (display_errors=off?), but I'm getting
Fatal Error: Class 'CRM_Contact_BAO_Group' not found in /Applications/MAMP/htdocs/drupal5/modules/civicrm/CRM/Contact/Form/Task/SaveSearch.php on line 103